Processing coffee beans to produce a beverage includes the steps of roasting, grinding and extracting. The selected granule size (course or fine) of the ground coffee can depend on the method utilised to brew or extract the coffee. When extracting coffee (for example to produce espresso), a fine coffee grind can be produced immediately prior to extraction. The fineness of the ground coffee beans facilitates an increase in pressure during extraction and assists to produce a crema. The granule size of the ground coffee beans, freshness of the coffee beans, quantity of the ground coffee beans, the length of extraction and the pressure of water during an extraction all affect the flavour of the extracted coffee. Producing a good quality coffee extraction can be an art form that takes years to master.
Known coffee grinders designed to produce finely ground coffee beans for use with extraction machines include a hopper, blades (conical burrs or flat burrs), a timer and a support for a portafilter. Ground coffee travels from the blades through a passage to the portafilter. A disadvantage of known coffee grinders is that about 5 to 15 grams of ground coffee beans is retained in the coffee grinder between extractions. This is particularly problematic as ground coffee quickly loses its volatiles (flavour and aroma) once ground and, if left for too long, becomes stale. When the retained ground coffee beans mix with freshly ground beans this can greatly affect the extraction process and the resultant flavour of the extracted coffee. To avoid this problem, some baristas constantly purge the grinder to remove this stale coffee before filling the portafilter. This results in large quantities of wasted coffee beans.
A further problem of known coffee grinders is the inconsistency of the dose (the quantity of ground coffee beans produced). Once heated, ground coffee beans clump together and can become suspended in the grinder between the blades and the exit chute. This retained ground coffee may be dislodged intermittently, thereby adding extra ground coffee to each dosage. The vibration of the grinder and the action of collapsing (knocking the grouphead to settle the ground coffee beans) also causes this retained coffee to drop into the portafilter. Given that tenths of a gram of ground coffee affects the extraction process, the retained coffee can also affect the flavour of the extracted coffee.
Known grinders use flat burr or conical burr blades. A problem with these blades is that they overheat with frequent use. The motor may also be located directly below the blades, which further accentuates the problem of overheating.
The above references to the background art do not constitute an admission that the art forms part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the coffee grinder as disclosed herein.